This invention has to do with tank drain assemblies particularly suited to swimming pool filter applications and other applications where a particulate, regenerable filtering medium is disposed in a tank and a series of collector tubes extend into the filtering medium to collect filtered water therein for conveyance to a common drain port. More particularly, the invention is concerned with an improvement in the locking structure holding such collector tubes to the manifold surrounding the common drain port.
Swimming pool filters and like filters for substantially continuous use in filtering an aqueous medium comprise a tank having an inlet at the top and an outlet or common drain port at the bottom. Disposed within the tank is a filtering medium such as sand or diatomaceous earth. The water is spread upon the bed of filtering medium and percolates through the medium, giving up particulate and gelatinous contaminants in the process. A series of collector tubes are provided, distributed through the filtering medium, their perforate sides downward to preclude blocking by the filtering medium and to receive filtered water. These collector tubes are connected and held in radial relation to the filter tank by a common port manifold wall which combines the filtered fluid from the several collector tubes and conveys it to the common port for recirculation back to the swimming pool or other use. Such filters are periodically regenerable by backwashing, in which operation water is reversed through the system to flush contaminants from the filtering medium to waste.
It often occurs, during original installation or during replacement of the filtering medium after substantial periods of use, that the collector tubes, which are generally fabricated of a plastic material impervious to chemicals and water, are broken or damaged during the course of handling of the equipment or pouring of heavy sand into the filter tank. When a collector tube is broken off, it generally is broken off at the inner end, that is, the end which is held in the socket of the drain port manifold.